The specific aim of the project continues to be a better understanding of the mechanism of salt and water retention in congestive heart failure. Toward this aim we are working with Dr. Edgar Haber of the Massachusetts General Hospital on a simple and rapid radioimmunoassay of catecholamines in order to study the role of the sympathetic nervous system during the development of failure in the conscious dog. We have also started to study the protein metabolism as related to the cachexia of the dogs in failure. Factors regulating renin released in the isolated rat kidney will continue to be explored with particular emphasis on divalent cations and ADH. Evaluation of the 50,000 feet of motion picture film on the vascular-tubular relations in the human kidney will be continued, as will be the exploration of the localization of the Na-K-ATPase in the renal tubule, in particular the region of the macula densa, and the effect of diuretic agents on the enzyme. BIBLIOGRAPHIC REFERENCE: Watkins, L., Jr., Burton, J.A., Haber, E., Cant, J.R., Smith, F.W. and Barger, A.C.: The renin-angiotensin-aldosterone system in congestive failure in conscious dogs. J. Clin. Invest. 57: 1606-1617, 1976.